One of the main objects of the aromatization of foodstuffs for instance is to restore the original quality and nature of the flavour, aroma and taste of a given foodstuff material. Very often in fact the organoleptic properties of foodstuffs particularly diminish or are somehow modified in the course of the processes of freezing and storage, or during the modifications, such as cooking or baking, to which the foodstuffs are subjected in order to yield an edible material.
In the past the aromatization was mainly achieved by using materials of natural origin. Nowadays, however, synthetic chemical compounds are used at an ever increasing rate. Said compounds possess the advantage of being available very often in unlimited quantities and at prices lower than those of the natural materials. Moreover, due to the fact that the flavouring character of a natural material is the result of the overall effect determined by the combination and interaction of each of its constituents, the effects achieved by said natural material are very often not as well reproducible as those obtained by the use of the pure synthetic compounds.
In the field of perfumery the man in the art has to solve a similar problem in attempting to reconstitute the olfactive notes of certain natural essential oils or extracts. The perfumer's creativity however is continually boosted by the finding of new synthetic compounds, the organoleptic properties of which will enable him to introduce unprecedented olfactive characters or nuances into new phantasy perfume compositions.
As a consequence, the problem that the chemical industry has to solve is to satisfy the increasing demand of organoleptically interesting chemicals in order to better suit the specific needs of flavourists and perfumers.
The process of the present invention provides a novel and technically original solution to the problem set by the synthesis of unsaturated cycloaliphatic ketones of formula I. These compounds have been prepared in the past by various synthetic methods which can be resumed as follows:
a. partial hydrogenation of the corresponding acetylenic derivatives [Swiss patent No. 498,795]; PA1 b. direct condensation of an organo-metallic derivative of propene with a cyclogeranyl derivative [Swiss patent No. 503,684]; PA1 c. cyclization of a "pseudo-ketone" by means of acidic cyclization agents [Swiss patent No. 503,685]; PA1 d. dehydrogenation of a cyclohexenic ketone to afford the corresponding cyclohexadienic derivative [Swiss patent No. 505,773]. PA1 i. affording the desired compounds only in poor yield and/or PA1 ii. using non easily accessible starting materials. PA1 a. containing an exocyclic double bond in position 2 of the ring and a triple bond in position 2', and wherein Y represents an oxygen atom or an --OH group and a hydrogen atom, each of the substituents R represents a lower alkyl radical containing from 1 to 6 carbon atoms and n stands for zero; or PA1 b. containing a double bond in position 1 of the ring and a double bond in position 2', and wherein Y represents an oxygen atom, each of the substituents R represents a hydrogen atom and n stands for 1.
The above indicated methods have the disadvantage of
The process of the present invention does not offer the said disadvantages and, as a consequence, it can be conveniently exploited by the chemical industry.